I don't see anything wrong with a Yuri anyway, if two people are in love then that is fine. Pokemon made Harley out to be gay and that was fine.
You can also consider what animation aimed at chrildren that originates in America has included.
Captain Planet for example has an episode about Aids. Although it was caused by a blood transfusion in this particular episode usually when people think of Aids they think of drug use and unprotected sex.
Arthur: It has made a reference to South Park before. A children's program that references a show that focusses on being offensive.

There are plenty more examples out there of American children's animation including slightly controversial subjects so what is so bad about a yuri? In addition to this Sailor Moon actually looks like it is aimed at a slightly older audience than Arthur is so I see no need to have a problem with a yuri.